Centrifugal pumps



Dec. 6, 1966 F. w. Buse ETAL 3,289,598

CENTRIFUGAL PUMPS INVENTORS SAMUEL H. WEAVER FREDERICK W Bl/.SE

H6., 3 @am www ATTORNEY Dec. 6, 196e Filed Oct. 2l, 1965 *L* RADIAL LOAD(LBS.)

F. w. Buse ETAL 3,289,598

CENTRIFUGAL PUMPS 2 Sheets-Shefft E'.

222i SPL/UER r, INVENTORS ,f SAMUEL H. WEAVER FEEDER/CK n4 BUSE QM w TwATTORNEY United States Patent Otice 3,289,598 Patented Dec. 6, i9663,289,598 CENTRIFUGAL PUMFS Frederic William Buse, Bloomsbury, andSamuel H. Weaver, Phillipsburg, NJ., assiguors to Ingersoll-RandCompany, New York, NSY., a corporation of New Jersey Filed Oct. 21,1965, Ser. No. 499,838 7 Claims. (Cl. 10S- 103) This invention relatesto centrifugal pumps having a volute-shaped discharge chambersurrounding the irnpeller.

A centrifugal pump containing a single volute-shaped discharge chambercreates high unbalanced radial loads on the impeller which makes itnecessary to use large, heavy shafts and bearings in such pumps towithstand these loads. In order to reduce these unbalanced radial loads,pump designers have used the twin volute type of centrifugal pump whichcontains an internal wall known .as a splitter extending around theimpeller for about 180 degrees and dividing the annular chambersurrounding the impeller into two volute chambers. Generally, thissplitter is cast integrally into the pump housing.

While the use of a 180 degree or full splitter greatly reduces theunbalanced radial loading on the pump impeller, it creates otherproblems. For example, a pump containing `a splitter has a larger andheavier housing than an equivalent pump of the single volute design.Secondly, the casting of the splitter integrally with the housing isdifficult because the portions of the mold forming the splitter must beaccurately held by special core supports. Notwithstanding these coresupports, such portions frequently shift during molding causing spoilageof the resulting casting. Another problem is caused by the fact that thesplitter extends around the housing for about 180 degrees which makes itdicult to inspect, clean and smooth or grind the surfaces of the castinghidden by the splitter. Finally, centrifugal pump housings generallycomprise a pair of separable half-sections for convenience of assemblyof the pump. In such pumps, a full splitter will extend over portions ofboth half-sections which makes it necessary for the portions of thesplitter in both half-sections to be aligned in the assembled housing.The need of alignment of the splitter portions further increases theneed for accuracy in the positioning of the splitter in the housingduring the casting process.

The principal object of this invention is to eliminate or substantiallyminimize the objections and problems encountered with the use of theconventional centrifugal pump design employing a splitter.

Other important objects of this invention are: to provide a centrifugalpump having a splitter which is easy to cast `and which makes it easy toinspect, clean, and grind surfaces of the housing hidden by thesplitter; to provide a pump design employing a splitter which does notrequire matching of the portions of the splitter in the separate halvesof the pump housing; and to provide a centrifugal pump design whichsubstantially reduces the amount of unbalanced radial loading on theimpeller without substantially increasing the size of the pump casing.

In brief, the objects of this invention are attained by limiting orshortening the splitter to extend over an angle of much less than 180degrees, forming the shortened splitter wholly in one of the pump casinghalves and locating the shortened splitter in the casing where itgreatly reduces the unbalanced radial loading on the impeller when thepump is operating under normal lluid output conditions.

The invention is described in connection with the accompanying drawingswherein:

FIG. l is a side elevation of a centrifugal pump made in accordance withthe disclosed invention;

FIG. 2 is an enlarged section of the centrifugal pump shown in FIG. land taken across the axis of the impeller;

FIG. 3 is a fragmentary enlarged section taken on the line 3 3 of FIG.2;

FIGS. 4, 5 and 6 are diagrammatic sectional views illustratingcentrifugal pumps employing, respectively, a 180 splitter, a 90 splitterand a 221/2 splitter; and

FIG. 7 is a curve illustrating the change in unbalanced radial loadsapplied to the impeller in each of the pumps shown in FIGS. 4, 5 and 6as a function ofthe pump output,

The centrifugal pump 1 shown in FIGS. l to 3 includes an outer housingor casing 2 formed by a pair of separable halves, including an upperhalf 3 and a lower half 4, fastened together by bolts 5. The housing 2is mounted on a base 6 land contains a fluid inlet 7 and a dischargeoutlet 8, both of which are formed in the lower half 4 of the housing 2.A pump impeller 9 is mounted in the housing 2 on a shaft 10 and containsa series of pumping varies 11. The housing 2 forms a volute-shapedchamber 12 surrounding the circumference 14 of the impeller 9 and havinga cutwater area 15 located at its small end and a throat area 16 at itslarge end. All of the foregoing structure is conventional in thecentrifugal pump art.

This invention resides in providing a splitter partition 18 in thechamber 12 to divide the space in the chamber adjacent the splitter 18into two portions, including an outer space 19 located outside thesplitter 18, and an inner space 2i) located on the inside of thesplitter 18 between it and the impeller circumference 14. The splitter18 is formed in the upper half 3 of the housing 2 and is positioned sothat the cross-sectional area of the outer space 19 remainssubstantially constant along the length of the splitter 18. The innerspace 20 has a volute shape extending in the direction of the length ofthe splitter 18, as illustrated in FIG. 2.

The splitter 18 illustrated in FIG. 2 extends over an angle of about Ingeneral, the angular length of the splitter 18 can vary between aminimum of about 221/2 and a maximum of about The inlet end 22 of thesplitter 18 will begin at a point located approximately diametricallyopposite the cutwater area 15 of the chamber 12. Both the inlet end 22and the outlet end 23 of the splitter 18 are tapered to reduce llowlosses caused by turbulence.

It will be noted that the splitter 18 is located wholly within the upperhalf of the housing 2. This eliminates the need for matching or aligningtwo splitter portions located in separate halves of the housing which`is the case in the prior art using a splitter. Furthermore, the splitter18 is short enough for hidden internal surfaces located in the housingbehind the splitter to be easily inspected, cleaned and smoothed orground whenever necessary.

The radial load curves of pumps having a 221/2 splitter and a 90splitter are illustrated in FIG. 7. Each of these curves have a verticalaxis indicating the unbalanced radial load on a `pump impeller and ahorizontal axis indicating pump output in gallons lper minute. Inaddition, FIG. 7 illustrates a curve showing the operation of a pumphaving `a full or 180 splitter. FIGS. 4, 5 and 6 diagrammaticallyillustrate the various types of pumps having curves shown in FIG. 7.

In FIG. 7, it will be noted that the unbalanced radial load created by apump having a 221/2" splitter is rather high, when the pump output islow (a 221/2o splitter provides about 50% of the radial loading, at lowoutputs, created in a pump which does not have a splitter), and that itthen drops off to a load which is below the radial load created by apump having a 180 splitter in the vicinity designated by the verticaldashed line 25, located on the pump loutput axis of the curve. A pumphaving a 90 splitter creates a somewhat reduced radial load at lowoutput, compared to the pump with a 221/2 splitter, and then drops ofito a load well below the load curve produced by the pump having a 180splitter. The lowest load created by the pump having a 90 splitteroccurs in the region of the dotted line 26 located on the pump outputaxis.

As should now be obvious, when the pumps having the 221/2" splitter orthe 90 splitter are operated with pump outputs occurring in the `regionsgenerally indicated by the dotted lines 25 and 26, the unbalanced radialloads on the impeller are minimized and, in some cases, below that whichare applied to the impeller by a. pump having a 180 splitter. It hasbeen found that the maximum efliciency of pumps having reducedsplitters, in accordance with this invention, occurs in the vicinity ofthe output values which correspond to the reduced radial loads on theimpeller. For example, both of the pumps containing 221/2" and 90splitters have a maximum eiciency when operating in the vicinity of thedotted line 27 located along the pump output axis.

The invention in this case is believed to be the discovery that a pumphaving a greatly shortened or reduced length splitter, of much less than180, can provide a large reduction in unbalanced radial loading on theimpeller of a centrifugal pump at all pump output conditions. When apump is operated at a point on its output curve providing maximum pumpefficiency, which is generally its normal operating output, a shortenedsplitter provides substantially the same or better results than a 180splitter when the pump is delivering its normal output or capacity. Inaddition, even when a pump is normally Operated at a reduced output,less than an output providing maximum e'iciency, la shortened splitteroften reduces the radial loading on the impeller enough to make itunnecessary to use heavier shafts and bearings in the pump. In caseswhere the higher radial loads of a shortened splitter can be tolerated,it is believed that the many advantages provided by the shortenedsplitter are sufficiently attractive to justify its use in place of afull splitter.

While only a single embodiment of the invention is described andillustrated in detail, this invention is not limited simply to thedescribed embodiment, but contemplates other embodiments and variationswhich utilize the concepts and teachings of this invention.

Having thus described our invention, we claim:

1. A centrifugal pump comprising:

an impeller;

a casing surrounding the impeller and containing a volute-shaped chamberextending around the circumference of the impeller and including acutwater a-rea at one end and a throat outlet area at the other end;

`said casing being divided into two halves for purposes of assembly ofthe pump;

one of said halves containing said cutwater area; and

a splitter partition located in said volute chamber and wholly containedin the other of said casing halves for dividing the discarge flow of theimpeller into two paths extending along a portion of said voluteChamber.

2. The pump of claim 1 wherein:

said splitter partition has an inlet edge located in said casingsubstantially diametrically opposite said cutwater area of said volutechamber.

3. The pump of claim 2 wherein:

the area of said chamber located on the outside of said splitterpartition remote from said impeller is substantially constant in crosssection throughout the length of said splitter partition.

4. The centrifugal pump of claim 3 wherein:

the area on the inside face of the splitter partition adjacent theimpeller forms a smaller volute chamber extending along the length ofthe splitter partition.

5. The pump of claim 4 wherein:

said splitter partition is located so that the pump fluid dischargedfrom both sides of the splitter has substantially the same velocity.

6. The pump of claim 5 wherein:

said splitter partition extends along the circumference of said impellerover an angle located in a range extending between substantially 221/2"and substantially 1 7. A centrifugal pump comprising:

an impeller;

a casing surrounding the impeller and containing a volute-shaped chamberextending around the circumference of the impeller and including acutwater area at one end and a throat outlet at the other end oppositesaid cutwater area;

a splitter partition located in said volute chamber approximately midwaybetween said cutwater area and said throat outlet and extending over anangle located in a range extending between substantially 221/2 andsubstantially 90;

said splitter partition being curved generally in the direction of saidvolute chamber and extending substantially parallel to the outerperipheral wall of said casing defining said volute chamber; and

said splitter partition being circumferentially spaced from said throatoutlet by a portion of said voluteshaped chamber forming a singlepassage which is bordered by said casing and said impeller and receivesfluid discharged from both the inner and outer faces of said splitterpartition.

References Cited by the Examiner UNITED STATES PATENTS 111,026 1/1871Williams 103-103 126,639 5/1872 Leifel 103-111 1,390,391 9/1921 Skidmore103-111 2,764,944 10/1956 Lawrence 103-111 2,849,960 9/1958 Olmstead etal. 103-111 2,955,540 10/1960 Pawlicki 103-111 FOREIGN PATENTS 687,3112/ 1940 Germany 7,730 4/ 1905 Great Britain. 407,5 68 11/ 1944 Italy.

MARK NEWMAN, Primary Examiner. HENRY RADUAZO, Examiner.

1. A CENTRIFUGAL PUMP COMPRISING: AN IMPELLER; A CASING SURROUNDING THEIMPELLER AND CONTAINING A VOLUTE-SHAPED CHAMBER EXTENDING AROUND THECIRCUMFERENCE OF THE IMPELLER AND INCLUDING A CUTWATER AREA AT ONE ENDAND A THROAT OUTLET AREA AT THE OTHER END; SAID CASING BEING DIVIDEDINTO TWO HALVES FOR PURPOSES OF ASSEMBLY OF THE PUMP; ONE OF SAID HALVESCONTAINING SAID CUTWATER AREA; AND A SPLITTER PARTITION LOCATED IN SAIDVOLUTE CHAMBER AND WHOLLY CONTAINED IN THE OTHER OF SAID CASING HALVES